After World War II, Korea was divided at the 38th parallel. The south was occupied by the US, while the north was occupied by the Soviet Union. At the time, there was a huge controversy in Korea over whether to keep the grossly inequitable land ownership system, which made most Koreans poor tenant farmers subject to a small ruling class. Rhee, who was now 70 years old, was supported by the American government as a right-wing counterweight to the Soviets' favorite leftist son, Kim Il Sung. Left-wing groups in the south boycotted his election in 1948, so he won easily.

Rhee was a hawk: he had to be a hawk in order to stand up to Kim. Before the Korean War broke out, Rhee ordered many small attacks on North Korean forces across the border, and used the army to put down socialist rebels in his own territory. As early as 1949, he had definite plans to invade the North, although US secretary of stateDean Acheson warned him that such an invasion would not be supported by the U.S.

Although he took a back seat to Douglas MacArthur during the war, Rhee resurfaced in the aftermath. Because he wanted to unify Korea, he was a bitter opponent of the truce negotiations in Kaesong and Panmunjom, and he tried to derail the process by releasing thousands of POW's against their will. The US considered staging a coup to get rid of him, but never followed through.

After the war, the Korean economy was a wreck, and despite a deluge of American aid, Rhee's administration couldn't do much with it. In the elections of 1960, he was near defeat, but manipulated the tally so that he would win. When this became public, South Korea erupted in a firestorm of demonstrations, and Rhee was forced to resign.